EP0315388B1 - Procédé et dispositif de traitement d'une suspension de fibres - Google Patents

Procédé et dispositif de traitement d'une suspension de fibres Download PDF

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Publication number
EP0315388B1
EP0315388B1 EP88310201A EP88310201A EP0315388B1 EP 0315388 B1 EP0315388 B1 EP 0315388B1 EP 88310201 A EP88310201 A EP 88310201A EP 88310201 A EP88310201 A EP 88310201A EP 0315388 B1 EP0315388 B1 EP 0315388B1
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EP
European Patent Office
Prior art keywords
pulp
treatment
filtrate
fiber suspension
liquid
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP88310201A
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German (de)
English (en)
Other versions
EP0315388A2 (fr
EP0315388A3 (en
Inventor
Pasi Immonen
Raimo Kohonen
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Ahlstrom Corp
Original Assignee
Ahlstrom Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ahlstrom Corp filed Critical Ahlstrom Corp
Priority to AT88310201T priority Critical patent/ATE73509T1/de
Publication of EP0315388A2 publication Critical patent/EP0315388A2/fr
Publication of EP0315388A3 publication Critical patent/EP0315388A3/en
Application granted granted Critical
Publication of EP0315388B1 publication Critical patent/EP0315388B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21D—TREATMENT OF THE MATERIALS BEFORE PASSING TO THE PAPER-MAKING MACHINE
    • D21D5/00—Purification of the pulp suspension by mechanical means; Apparatus therefor
    • D21D5/02—Straining or screening the pulp
    • D21D5/04—Flat screens
    • D21D5/046—Rotary screens

Definitions

  • the present invention relates to a method and apparatus for treating fiber suspension, in which method fiber suspension is fed to a pressurized treatment apparatus and in which the treatment is carried out under overpressurized conditions in an airless space.
  • the method in accordance with the invention is applied to a new type of disc filter treatment apparatus, which is developed to operate in a pressurized state.
  • drum-type filters see e.g. WO-A-85/04433
  • thickeners and screens of the known pulp treatment apparatuses have generally been pressurized.
  • the advantages achieved by them have been, for example, the space saved at the mills, a specific capacity which is considerably higher than that of the unpressurized apparatuses and the airlessness of the treatment space of the pulp, whereby the quality of the pulp remains better. It may even be considered that the capacity of a whole mill could be increased if the old unpressurized treatment apparatuses were to be replaced by new type of apparatuses operating with larger pressure differences.
  • drum-type pulp treatment apparatuses operating with overpressure have the same problems as the other drum-type apparatuses in other words, for example, when used as a filter a long retention time of the so called cloudy water in the treatment means before its possible return back to the means to be cleared.
  • fiber suspension is normally fed to the outer rim of the filter surface and the filtrate is discharged through the longitudinal channels of the cylinder inside the filter surface, which are connected with each sector of the cylinder and, further on, through valve members at the end of the cylinder. If the cloudy liquid is desired to be returned back to the cylinder to be cleared, it has to be taken into consideration that the liquid has flowed long along channels which are several meters long to the end of the drum and from there further to the feed point.
  • the filter has to be installed to said level to which the whole amount of the pulp to be treated has to be pumped.
  • a second alternative for developing underpressure is naturally to use a vacuum pump, which however also adds costs. Additionally, the use of underpressure is restricted by the temperature of the fiber suspension to be treated, which may not rise over 80-90°C, because due to the underpressure the liquid would start to boil on the underpressure side. Also the maximal pressure difference is 101 kPa which, as commonly known, cannot be exceeded.
  • the apparatus comprises conventional filter disc units mounted on the shaft, which units are arranged inside a casing which can be pressurized.
  • the pressure difference is effected by a blower by which a desired overpressurized gas layer is generated in the upper part of a pressure vessel.
  • the apparatus according to said U.S. patent includes also a control system by which the size of the gas layer is maintained as desired, in other words substantially the same as in conventional disc filters.
  • a method of treating fiber suspension in a disc type pulp treatment apparatus into which the fiber suspension to be treated is fed pressurized and from which the pulp is discharged, characterized in that said treatment apparatus is filled up with the mixture to be treated so that the treatment is carried out in a closed airless space under pressurized conditions.
  • an apparatus for treating pulp which apparatus mainly comprises a pressure-proof casing, a shaft rotating inside the casing and discs arranged on the shaft, which discs are formed from sectors with filter surfaces, between which surfaces there is a liquid compartment which communicates with the liquid discharge means, characterized in that the annular surface formed by a sequence of sectors provided with filter surfaces is divided into two or more portions separated from one another by members which are stationary relative to the casing, and which members separate the different treatment stages of fiber suspension from one another.
  • the pulp treatment apparatus 1 in accordance with the present invention mainly comprises discs 5, which are formed by sectors 4, arranged on a shaft 3, all being located within a substantially pressure-proof casing 2.
  • the sectors 4 are mounted on the shaft 3 in such a way that in shaft 3 each sector has its own discharge/inlet duct 6, which communicates with a liquid compartment 7 of each sector, which is defined in a known way by filter surfaces.
  • the fiber suspension to be treated is fed in a pressurized manner into the interior of the casing 2 so that the space within the casing is filled with suspension.
  • the retention time of the filtrate of an apparatus in accordance with the present invention is, for example, in thickening use very short.
  • the liquid When guiding the filtrate liquid via the shaft out of the sectors, the liquid must, at its maximum, flow only along the length of the shaft to reach valve moans located outside the apparatus, wherefrom the liquid is transferred for further treatment.
  • the cloudy and clear filtrate there is no time for the cloudy and clear filtrate to be mixed with each other, and the amount of cloudy filtrate, which may possibly be returned to the apparatus, hardly differs from the actual amount of the cloudy filtrate.
  • Figs. 1 and 2 disclose an embodiment for removing the pulp cake from the sectors.
  • sealing members are arranged at least at one point on the rim of disc 5 by which the pressure inside the casing is prevented from discharging to the loosening point of the pulp cake.
  • the sealing member in the arrangement shown in Fig. 1 comprises a sector-like plate 8, in the middle of which there is an opening 9 which is larger than the filter surface of the disc sector, through which opening 9 the pulp cake is dropped or transferred to be further treated.
  • the plates 8 of two adjacent discs form a space 10 separated from the rest of treatment apparatus and opening (in the case of the figure) downwardly, through which space the pulp cake is discharged from the treatment apparatus.
  • the space inside casing 2 in the area of plates 8 has no fiber suspension at all.
  • the size of the plates 8 depends on the sectors 4 of the disc 5 in such a way that plate 8 seals the inner space of casing 2 in all angle positions of the disc in such a way that the pressure cannot enter discharge space 10.
  • space 10 is, of course, also sealed on the side of shaft 3 either by a curved or a straight plate 11.
  • Fig. 3 shows a disc sector 40 of a preferred embodiment, which comprises a middle portion 41 with filter surfaces, and edge portions 42-45, which are raised relative to the middle portion, the outermost plane of which, relative to the wire surface, forms a sealing surface with the surface of the plate 8 on the disc side shown in the previous figures.
  • the filter surface 41 of each sector 40 in a way forms the bottom surface of compartment 46, in which compartment the pulp cake is formed when the apparatus operates as a thickener.
  • the height of the edge portions is advantageously defined in such a way that even in a maximum thickening process the thickness of the pulp cake does not exceed the height of the edge portions, in other words the pulp cake never touches the surface of plate 8. This is required, because otherwise the friction between the pulp cake and plate 8 would rapidly raise the energy consumption of the apparatus.
  • the unbroken surface of plate 8 on both sides of opening 9 must be at least of the same size as sector 4 of disc 5 to prevent the pressure from escaping.
  • high treatment pressure it is advantageous to arrange a broader unbroken portion on the plate, whereby one sealing surface does not have to bear the stress alone.
  • high treatment pressures it may be necessary to arrange more removal and discharge points for the pulp cake on the rim of the disc, because the formation speed of a pulp cake is high. Thus by arranging several discharge points it is possible to reduce the rotational speed of the discs.
  • Fig. 4 shows a preferred embodiment of the apparatus in accordance with the present invention, which is mainly aimed to be used for the recovery of so called zero fiber, in other words the fine dry substance which has been drawn in with the water removed from the web in a paper machine, or for like purpose.
  • the surface of each disc is divided into several portions, in other words treatment stages 21, 22, 23 by plates 24, 25 and 26 operating as sealing members.
  • Long stock is fed into portion 21, which stock forms the so called basic stock on the wire surfaces, in other words a fiber layer which operates as a filter medium for the actual zero fiber being thickened, and on which the pulp cake is formed from the pulp including zero fibers.
  • the sealing member in other words the plate 24 separates portion 21 from the actual thickening portion 22, which (in the case of the figure) is about 250 grades from the disc surface.
  • the sealing member 25 separates portion 23 of the disc from thickening portion 22. Portion 23 is used to remove the pulp cake from the filter surface and the cake is discharged by transfer devices 27 further on.
  • Discharge portion 23 is separated from the formation portion 21 for the basic stock by plate 26.
  • each sealing member must have an annular breadth of at least the same size as the sector of the disc so as to fulfil the minimum requirements of sealing. If one desires to improve the sealing, said breadth of the sealing surface should advantageously be a multiple of the breadth of the disc sector. It may also be seen in the figure that the sealing members may be separated relative to one another or also in an embodiment they may form a uniform plate surface which has openings for the infeed and for the discharge of the pulp cake.
  • Fig. 5 shows a scheme for the use of the apparatus of Fig. 4 for filtering zero water.
  • Auxiliary pulp i.e. long stock, is fed from conduit 31 to the portion 21 of apparatus 1 of Fig. 4 for formation of the basic stock, and zero water is fed from conduit 32 for the actual thickening zone (22, Fig. 4).
  • the initial filtrate 33 from the formation portion of the basic stock is guided through the infeed of zero water back to filtering apparatus 1, from which the clear filtrate is gathered from conduit 34.
  • the filtrate from conduit 34 may be used for this purpose by taking part of it and by feeding it through pump 35 and conduit 36 back to the treatment apparatus.
  • the removal of the pulp cake may be carried out from the inside of the sectors of the disc by guiding the shower water along the liquid discharge ducts of the shaft in the opposite direction relative to its conventional direction.
  • a third principle alternative is, of course, different scraper arrangements, which may be arranged to wipe the wire surface when it is at the discharge opening, and to rise higher when the edge protrusions of the sectors pass under the scrapers.
  • Fig. 6 shows yet another embodiment of the apparatus in accordance with the present invention, in which an additional sealing element 28 and a pulp treatment element 29 have been added to the apparatus as compared to Fig. 4.
  • the sealing element 28 is similar to the previously described sealing elements, but element 29 may be used, for example, for the finishing drying of the pulp cake by blowing drying gas into the compartment so that the gas displaces liquid in the pulp cake. Such method is used when a high dry substance content is desired and the penetration of gas into the pulp does not cause any harm.
  • washing also in such a way that the filtrate utilized to operate as washing liquid in each washing stage is not the filtrate of the immediately following stage, but that of some other following stage, whereby the difference in level of cleanliness between the washing liquid and the suspension to be treated is greater and the washing effect of the liquid is somewhat more efficient.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Paper (AREA)
  • Treatment Of Fiber Materials (AREA)
  • Investigating Or Analysing Biological Materials (AREA)
  • Medicines Containing Material From Animals Or Micro-Organisms (AREA)
  • Polysaccharides And Polysaccharide Derivatives (AREA)
  • Preliminary Treatment Of Fibers (AREA)

Claims (20)

1. Procédé pour traiter de la suspension de fibres dans un dispositif de traitement de la pâte à papier brute du type à disques (1), dans lequel la suspension de fibres devant être traitée est amenée sous pression et à partir duquel la pâte à papier brute est évacuée, caractérisée en ce que ledit dispositif de traitement (1) est rempli du mélange devant être traité de manière que le traitement soit effectué dans une enceinte fermée dépourvue d'air dans des conditions sous pression.
2. Procédé selon la revendication 1 caractérisé en ce que la surface en forme de disque sensiblement annulaire du dispositif de traitement est divisée mécaniquement en deux portions au moins (21, 22, 23 ; 29) qui forment un nombre correspondant de stades de traitement et en ce que une première suspension de fibres (A) est délivrée au premier stade de traitement (21) à partir duquel le filtrat obtenu est délivré avec une seconde suspension de fibres (B) au second stade de traitement (22), à partir duquel le filtrat est déchargé et la pâte traitée est transformée au stade suivant (23, 29).
3. Procédé selon la revendication 2 caractérisé en ce que une partie est séparée du filtrat résultant, à l'aide duquel le gâteau de pâte est enlevé de la surface de la toile métallique (41) dans le dernier stade de traitement (23).
4. Procédé selon la revendication 2 ou 3 caractérisé en ce que la première suspension de fibres (A), qui est une suspension de fibres longues de qualité élevée, est délivrée au premier stade de traitement (21) pour former la pâte de base sur la surface de la toile métallique (41), afin que la matériau en fibres fines dans ce qu'il est convenu d'appeler le matériau sans eau, en cours d'alimentation en tant que seconde suspension de fibres (B) dans le second stade de traitement (22) peut être épaissi à la fois sur la pâte de base et dans la pâte de base elle-même.
5. Procédé selon la revendication 1 caractérisé en ce qu'une première suspension de fibres est délivrée avec une seconde suspension à un premier stade de traitement, les premières zones de ce dernier fournissant un filtrat qui est ramené en recyclage vers le premier stade de traitement avec lesdites suspensions de fibres.
6. Procédé selon la revendication 5 caractérisé en ce que la suspension de fibres traitée dans le premier stade est déchargée du dispositif de traitement dans le second stade en utilisant le filtrat clair obtenu à partir des zones finales du premier stade de traitement.
7. Procédé selon la revendication 5 ou 6 caractérisé en ce que, en même temps que de la pâte auxiliaire est délivrée en tant que première suspension de fibres pour la formation de la couche de pâte de base sur les surfaces de la toile métallique, du matériau démuni d'eau est délivré en tant que seconde suspension de fibres, de manière à obtenir un filtrat trouble à l'extrémité frontale dudit stade de traitement, ce filtrat étant ramené pour recyclage vers ledit stade en même temps que la première et la seconde suspension de fibres.
8. Procédé selon la revendication 1 caractérisé en ce que de la suspension de fibres est délivrée à un stade de traitement (22), dans lequel du liquide se sépare de la suspension et on laisse se former un gâteau de pâte sur la surface du filtre, et en ce que le gâteau de pâte ainsi formé est transféré vers le stade de traitement suivant (29), durant lequel le gâteau de pâte est soumis à un déplacement par gaz sous pression, ou similaire, de manière à intensifier l'évacuation du liquide du gâteau de pâte, ce gâteau de pâte étant ensuite transféré vers le stade de traitement suivant (23) ou il est expansé à partir de la surface du filtre et transféré au delà de ce dernier.
9. Procédé selon la revendication 1, caractérisé en ce que la suspension de fibres est délivrée à un premier stade de traitement, dans lequel du liquide de lavage est délivré à la suspension, ce liquide étant filtré lors du stade du traitement suivant puis la suspension de fibres est transférée aux stades de traitement suivants auxquels le filtrat du stade suivant dans l'ordre du traitement est amené de manière à servir de liquide de lavage.
10. Procédé selon la revendication 1 caractérisé en ce que la suspension de fibres est délivrée à un premier stade de traitement dans lequel le filtrat d'un troisième stade de traitement est délivré de manière à faire office de liquide de lavage, ensuite de la suspension de fibres est transférée au stade de traitement suivant auquel un filtrat des stades faisant suite au troisième stade est respectivement amené pour servir de liquide de lavage.
11. Dispositif pour traiter de la pâte à papier brute qui comprend essentiellement une enveloppe étanche à la pression (2), un arbre (3) tournant à l'intérieur de l'enveloppe et des disques (5) disposés sur l'arbre (3), les disques sont constitués de secteurs (4) avec des surfaces filtrantes, entre lesquelles il existe un compartiment de liquide qui communique avec des moyens d'évacuation de liquide, caractérisé en ce que la surface annulaire formée par une conséquence de secteurs (4) munis de surfaces filtrantes est divisée en deux ou plusieurs portions (21, 22, 23 ; 29) séparées les unes des autres par des éléments (24, 25, 26 ; 28) qui sont fixes par rapport à l'enveloppe (2), ces éléments séparant les uns des autres les différents stades de traitement d'une suspension de fibres.
12. Dispositif selon la revendication 11 caractérisé en ce que les éléments (24, 25, 26 ; 28) sont des éléments d'étanchéité qui peuvent séparer à la fois un ou plusieurs secteurs (4) des autres secteurs (4).
13. Dispositif selon la revendication 12 caractérisé en ce que des secteurs (4 ; 40) sont formés par deux surfaces filtrantes opposées (41) qui sont délimitées par des portions d'arêtes (42, 43, 44, 45), sur chaque côté.
14. Dispositif selon la revendication 13 caractérisé en ce que les portions d'arêtes (42 - 45) s'étendent vers l'extérieur du niveau de la surface filtrante (41), formant un compartiment avec la surface filtrante, dans lequel le traitement de la pâte est réalisé ou dans lequel se forme le gâteau de pâte.
15. Dispositif selon les revendications 12 ou 14 caractérisé en ce que les plans extérieurs des portions d'arêtes (42-45) parallèles à la surface filtrante (41) forment, avec les surfaces sur le côté des secteurs des éléments (24, 25, 26, 28), un joint d'étanchéité, qui sépare les stades de traitement les uns des autres.
16. Dispositif selon la revendication 11 caractérisé en ce que les moyens d'évacuation pour le liquide comprennent des conduites de transfert (6) pour le filtrat, disposées en communication avec l'arbre (3) et un système de vanne disposé en communication avec ces conduites, l'écoulement du filtrat étant guidé par ladite vanne.
17. Dispositif selon la revendication 11 caractérisé en ce que les moyens d'évacuation pour le liquide comprennent une conduite disposée sur le bord extérieur de chaque secteur (4) et un système de vanne à l'intérieur de l'enveloppe (2) coopérant avec ladite conduite, l'écoulement du filtrat étant guidé par ledit système de vanne.
18. Dispositif selon la revendication 11 caractérisé en ce que les moyens d'évacuation pour le liquide comprennent un système de vanne disposé au point de jonction de chaque secteur (4) et l'arbre (3) et des conduites s'étendent au delà du système de vanne.
19. Dispositif selon la revendication 11 caractérisé en ce que les moyens d'évacuation pour le liquide comprennent des conduites (6) disposées en communication avec l'arbre (3) et un système de vanne disposé sur l'arbre (3) dans la partie médiane du dispositif, l'écoulement du liquide étant ultérieurement guidé par ledit système de vanne.
20. Dispositif selon la revendication 11 caractérisé en ce que le dispositif fonctionne soit en continu soit cycliquement.
EP88310201A 1987-11-05 1988-10-31 Procédé et dispositif de traitement d'une suspension de fibres Expired - Lifetime EP0315388B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT88310201T ATE73509T1 (de) 1987-11-05 1988-10-31 Verfahren und vorrichtung zur behandlung einer fasersuspension.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI874887 1987-11-05
FI874887A FI81725C (fi) 1987-11-05 1987-11-05 Foerfarande och anordning foer behandling av fibersuspension.

Publications (3)

Publication Number Publication Date
EP0315388A2 EP0315388A2 (fr) 1989-05-10
EP0315388A3 EP0315388A3 (en) 1989-05-31
EP0315388B1 true EP0315388B1 (fr) 1992-03-11

Family

ID=8525361

Family Applications (1)

Application Number Title Priority Date Filing Date
EP88310201A Expired - Lifetime EP0315388B1 (fr) 1987-11-05 1988-10-31 Procédé et dispositif de traitement d'une suspension de fibres

Country Status (6)

Country Link
US (1) US5073264A (fr)
EP (1) EP0315388B1 (fr)
AT (1) ATE73509T1 (fr)
DE (1) DE3869061D1 (fr)
FI (1) FI81725C (fr)
NO (1) NO884949L (fr)

Families Citing this family (8)

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Publication number Priority date Publication date Assignee Title
US5192454A (en) * 1987-11-05 1993-03-09 A. Ahlstrom Corporation Method for treating fiber suspension
SE463242B (sv) * 1989-03-13 1990-10-29 Hedemora Ab Filter foer kontinuerlig filtrering av suspension
US5934476A (en) * 1996-08-21 1999-08-10 Roe; Philippe Vacuum rotary filtration apparatus
FI106386B (fi) * 1999-05-03 2001-01-31 Valmet Corp Menetelmä ja laitteisto kuitujen talteenottamiseksi paperitehtaan kiertovedestä
DE102004033328A1 (de) * 2004-07-09 2006-02-09 Bhs-Sonthofen Gmbh Filter mit Feststoff-Resuspendierung
FI122775B (fi) 2004-09-07 2012-06-29 Andritz Oy Laite ja menetelmä massan käsittelemiseksi
SE528722C2 (sv) * 2005-06-03 2007-01-30 Metso Paper Inc Anordning för behandling av cellulosamassa i en tvättapparat anordnad med en förstärkande spant
AT505247B1 (de) * 2007-05-30 2009-01-15 Andritz Ag Maschf Vakuumunterstütztes entwässerungsverfahren und rotierender filter zur durchführung des entwässerungsverfahrens

Citations (1)

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Publication number Priority date Publication date Assignee Title
WO1985004433A1 (fr) * 1984-04-03 1985-10-10 Sunds Defibrator Aktiebolag Procede et appareil de traitement de materiaux en suspension

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US1649581A (en) * 1921-04-29 1927-11-15 United Filters Corp Method and means for removing filter cakes from filter mediums
US2115211A (en) * 1934-08-09 1938-04-26 Texas Co Continuous filtration of wax bearing oil
FR796609A (fr) * 1935-01-07 1936-04-11 Alsacienne Constr Meca Perfectionnement aux filtres
US2055119A (en) * 1935-02-16 1936-09-22 Karl R Clendening Starch mill reel
US2027652A (en) * 1935-04-25 1936-01-14 Municipal Sanitary Service Cor Filter
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BR5900592U (pt) * 1979-04-30 1980-11-04 Voith Sa Maquinas Equip Filtro de tambor celular para desaguar suspensoes
DE3020119A1 (de) * 1980-05-27 1981-12-10 Envirotech Corp., Menlo Park, Calif. Verfahren und vorrichtung zum waschen von vakuumfiltrierbaren materialien, insbesondere papierfaserpulpe
US4330405A (en) * 1980-09-29 1982-05-18 Davis Kent L Vacuum disc filter
FI68005C (fi) * 1980-09-30 1985-07-10 Rauma Repola Oy Foerfarande foer tjockning av massa eller suspension och skivfilter foer tillaempning av foerfarandet
FR2564003B1 (fr) * 1984-05-14 1989-06-23 Pechiney Aluminium Dispositif d'alimentation par ruissellement de filtres rotatifs a disques
SE451948B (sv) * 1985-05-02 1987-11-09 Hedemora Ab Filter for kontinuerlig filtrering under tryck av en suspension
JPH01222515A (ja) * 1988-03-02 1989-09-05 Matsushita Electron Corp 半導体集積回路装置

Patent Citations (1)

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Publication number Priority date Publication date Assignee Title
WO1985004433A1 (fr) * 1984-04-03 1985-10-10 Sunds Defibrator Aktiebolag Procede et appareil de traitement de materiaux en suspension

Also Published As

Publication number Publication date
FI81725C (fi) 1990-12-10
FI81725B (fi) 1990-08-31
EP0315388A2 (fr) 1989-05-10
FI874887A (fi) 1989-05-06
US5073264A (en) 1991-12-17
ATE73509T1 (de) 1992-03-15
NO884949D0 (no) 1988-11-04
EP0315388A3 (en) 1989-05-31
DE3869061D1 (de) 1992-04-16
FI874887A0 (fi) 1987-11-05
NO884949L (no) 1989-05-08

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